Palaeobiodiversity and Palaeoenvironments https://doi.org/10.1007/s12549-019-00390-7

ORIGINAL PAPER

Dapedium sp. from the Toarcian (Lower ) Úrkút Manganese Ore Formation (Bakony Mts., Hungary) and an overview of diversity of dapediiform

Márton Szabó1,2 & József Pálfy3,4

Received: 18 August 2018 /Revised: 10 November 2018 /Accepted: 28 May 2019 # The Author(s) 2019

Abstract Dapediidae are a characteristic group of deep-bodied Mesozoic actinopterygian fishes with a moderate diversity at genus- and species- level. Here, we add a new occurrence to their patchy fossil record and describe in detail a nearly complete dapediid specimen from the pelagic deposit of the Toarcian Úrkút Manganese Ore Formation in the Transdanubian Range of Hungary. The preserved characters represent nearly all anatomically important body parts and allow assignment to and comparison with other dapediid genera. This is the first reported occurrence of the order in Hungary and the Carpathian Basin that extends the known geographical range of the genus to the Mediterranean (western Tethyan) Jurassic. A review of the temporal distribution of published occurrences of dapediids permits speculation that the disappearance of exclusively Late genera, coincident with the end-Triassic extinction event, was likely related to their specialised feeding strategies and light or incomplete squamation. Multiple environmental crises (warming, acidification and anoxia) severely affected reefal habitats and favoured the survival of the generalist-durophagous Dapedium.The Úrkút specimen adds important data to the Early Jurassic, particularly Toarcian Lagerstätte-dominated fossil record of dapediids. In contrast to the end-Triassic, the Toarcian oceanic anoxic event did not lead to genus extinction among dapediids, possibly prevented by adaptations evolved during the preceding and similarly multi-stressor event. Continuing studies of Mesozoic specimens in Hungarian collections may provide new records and insights into other groups as well.

Keywords Dapedium . Toarcian . End-Triassic . Extinction . Diversity

Introduction interlocking rhomboidal ganoid scales, relatively small mouth, skull bones ornamented by ganoine-tubercles and ridges, hem- Dapedium Leach, 1822 is an extinct genus of lower shaped dorsal and anal fins, dorsal fins with more than 20 rays, actinopterygian fish, first discovered at , England. It and pronounced dorsal and ventral ridge scales (Thies and Hauff is characterised by a deep (hypsisomatic), disc-like body, 2011; Smithwick 2015; Thies and Waschkewitz 2015;Gibson 2016). The fossil record of Dapedium ranges from the late (Late Triassic) (Tintori 1983; Lombardo and Tintori 2005)tothe * Márton Szabó earliest Aalenian () (Thies and Hauff 2011; [email protected] Maxwell and López-Arbarello 2018). All confirmed occurrences have been reported from Europe; the only alleged Dapedium find József Pálfy from India (Jain 1973) has been disputed (Maxwell and López- [email protected] Arbarello 2018). The majority of the material originates from well-known Lagerstätten and strata with exceptional preservation 1 Department of Paleontology, Eötvös University, Pázmány Péter sétány 1/C, Budapest 1117, Hungary in England, France, Belgium, Italy and Germany (i.e. sites in the western Tethyan shelf or adjoining epicontinental seas). This list 2 Department of Palaeontology and Geology, Hungarian Natural History Museum, Ludovika tér 2, Budapest 1083, Hungary is augmented here with a find from a Toarcian black shale-hosted manganiferous ore deposit in Hungary, representing a relatively 3 Department of Geology, Eötvös University, Pázmány Péter sétány 1/C, Budapest 1117, Hungary deep, pelagic environmental setting. On the basis of tooth morphology and functional mor- 4 MTA-MTM-ELTE Research Group for Paleontology, Ludovika tér 2, Budapest 1083, Hungary phology of the jaw, Dapedium was interpreted as a Palaeobio Palaeoenv generalist well-adapted for generalist durophagy (Thies and Geological Survey of Hungary (MGSH) in the same condition Hauff 2011;Smithwick2015;Stumpfetal.2017). as originally illustrated. Főzy and Szente (2014, p. 170) figured Facultative durophagy may have helped Dapedium in times an additional specimen, which is also housed in the vertebrate of increased competition for food resources (Smithwick fossil collection of the MGSH. Mineralogical and geochemical 2015). Based on a spectacular find of a Dapedium stuck studies of the phosphoritic nodules that yielded the fish remains in a shell of a Lytoceras ammonite, scavenging mode of life from Úrkút were carried out by Polgári et al. (2004). was also suggested (Thies and Hauff 2011,fig.13B). The Úrkút Manganese Ore Formation that yielded the According to Thies and Hauff (2012), Dapedium was also dapediid specimen described here is a hitherto less known a prey for larger predators. source of exceptional preservation related to bottom water The order Dapediiformes (including only the family anoxia. The relation of the Úrkút manganese ore deposit to Dapediidae) was established by Thies and Waschkewitz (2015), the Toarcian Oceanic Anoxic Event (T-OAE or Jenkyns event, who separated dapediids from semionotiform fishes, to which Müller et al. 2017) is well-established (see overviews by Haas they were formerly attributed. However, the phylogenetic study 2012 and Polgári et al. 2016a, b). The biological productivity was restricted to Dapedium. Within Dapediidae, Thies and Hauff was high in the surface waters, but bottom waters were (2011) included seven genera (Hemicalypterus, Tetragonolepis, oxygen-deficient (Polgári et al. 1991). Paradapedium, , Dapedium, and ). Gibson (2016) referred an additional genus, Aetheolepis, to the family. In 2018, a ninth genus Scopulipiscis Geological setting was introduced and described by Latimer and Giles (2018). Since the late 1960s, several fish fossils have been reported The village of Úrkút is located in Veszprém County, in the south- from the Úrkút Magnanese Ore Formation in Hungary (see in ern Bakony Mountains, western Hungary (Fig. 1a). Manganese “Previous work” section). A few of these remains are now ore mining in the Bakony Mountains started here in the Úrkút housed in museum collections, including one specimen bearing Basin in 1917 and was terminated in 2016. The black shale- diagnostic characters of Dapediidae. The aim of the present study hosted Mn-oxide and carbonate ore body of Úrkút is among is to provide a detailed anatomical and taxonomical description the ten largest deposits in the world (Polgári et al. 2013). of this specimen. A summary of the available information allows The Úrkút Manganese Ore Formation occurs in a large area in us to consider the history of diversification of the group, with an the Úrkút Basin. Its thickness reaches 30 m in the western part of emphasis on the possible reasons for selective extinction and the basin, and exceeds 100 m in the north-western part of the survival of dapediiforms at the end-Triassic and Toarcian events. basin, it includes three ore beds (Polgári et al. 1991;Bíró2014). The Úrkút ore deposits occur in a NE-SW trending, ~ 12-km- long and 4- to 6-km-wide zone. The manganiferous ore conform- Previous work ably overlies the Pliensbachian cherty limestone of the Isztimér Formation (Polgári et al. 2012, 2013)(Fig.1b). The sequence Mesozoic fish remains from Hungary have been the subject of starts with ~ 0.5 m of Mn-oxide ore, overlain by 1.0 m of radi- only a few studies. Toarcian fishes, representing several spe- olarian clay marlstone. The main manganese ore body has a cies, are figured from the black shale facies exposed in the maximum thickness of 15 m and is made up of variously Réka Valley (Mecsek Mountains, southern Hungary) (Főzy coloured and finely laminated Mn ore. This unit is followed by and Szente 2014), but have not yet been studied in detail. ~ 10 m of radolarian clay marlstone and ~ 2.5 m of Dulaietal.(1992) identified only a single species, manganiferous clay marlstone. The uppermost part of the se- Leptolepis normandica. With the exception of the Réka quence consists of 2.5 m of radiolarian clay marlstone, and ~ Valley material, all other reports are based on isolated remains. 2.5 m of manganiferous clay marlstone. A discontinuous chert Although fossil fishes of the Úrkút Manganese Ore Formation layer (Cservár Flintstone Member) represents the closes part of have been known for more than 50 years, published information the formation (Bíró 2014). For further details on the geology and is restricted to only a few brief reports. A large specimen was stratigraphy of the Úrkút Mn ore deposit, see Szabó and found and figured by Cseh-Németh (1966)as“ganoidfishre- Grasselly (1980), Szabó et al. (1981), Grasselly and Pantó main” (note that this specimen is the subject of the present study). (1988),Polgárietal.(1991, 2012, 2013, 2016a, b), Pantó et al. Polgári et al. ( 2000)andPászti(2004) also figured this specimen ( 1996), Haas (2012)andBíró(2014). as a pycnodontid fish fossil. Pászti (2004) gave the first detailed account on the fish remains of the Úrkút Manganese Ore Formation, describing them as pycnodontiform and amiiform Material and methods fishes. However, from the three specimens figured by Pászti (2004), only Cseh-Németh’s(1966) specimen was found still Of the four Toarcian fossil fish specimens known from Úrkút, available in the vertebrate fossil collection of the Mining and the present study is focused on specimen V.10279 (Fig. 2), Palaeobio Palaeoenv

Fig. 1 a Location map of Úrkút. Black star symbol signs the locality. b Schematic geological structure of the Jurassic sediments of the Úrkút Basin (modified after Bíró 2014) housed in the vertebrate paleontological collection of the appear to be deformed. Throughout this work, the part and Mining and Geological Survey of Hungary (MGSH). The counterpart, and the elements preserved on them are consistent- exact stratigraphical level of the specimen is not known, and ly labelled as A and B, respectively. it was collected from Shaft III (Polgári et al. 2000). Due to oxidization of pyrite, specimen V.10279 started to Specimen V.10279 is a moderately well-preserved individu- disintegrate. Cyanoacrylate glue was used to reattach the related al, with a standard length of 233 mm (measured from the tip of parts. To avoid further oxidization, V.10279 was also treated with the snout to the end of the caudal musculature). The specimen is polyvinyl-butyral (PVB). For measuring the scale dimensions, laterally compressed and is embedded in a phosphoritic nodule ImageJ software (version 1.48) was used. With slight modifica- (available as part and counterpart of a splitted nodule), in which tions, the terminology of Thies and Hauff (2011)andThiesand it lies in left lateral aspect. Cracks run through the trunk and the Waschkewitz (2015) was followed in the anatomical description. skull, which most probably resulted from the breaking of the For assessment of the history of diversity of dapediiform nodule. Some bones can be observed on both halves, either as fishes, a comprehensive dataset was compiled from literature fragments or impressions. In some cases, this makes it hard to sources. It was checked against occurrence data deposited in distinguish some bones from one another, or precisely recon- the Paleobiology Database. struct their outline. About half of the skull bones can be exam- ined separately; the others are too poorly preserved or fragmen- tary for detailed description. The dermal cranial ossifications Systematic palaeontology show more or less natural arrangement. Although Dapedium typically has dermal skull bones ornamented by ganoine, this Class: Cope, 1887 ornamentation is not preserved on the skull, because of the Super Division: Müller, 1844 (sensu Grande, 2010) ’ specimen s general condition and the way the nodule was split. Division: Halecomorphi Cope, 1872 Also for preservational reasons, fine details of several important Order: Dapediiformes Thies and Waschkewitz, 2015 skull bones are lost, and some parts (e.g. the nasal region) Family: Dapediidae Lehman, 1966 Palaeobio Palaeoenv

(Fig. 3, RoNaAnt) cannot be properly observed. The exact position and shape of the anterior nasal opening (Fig. 3,ano) is uncertain. Therefore, it cannot be established whether the antorbital, the rostral and the nasal make up the out- line of the anterior nasal opening together, or only the rostral and the nasal. It is also uncertain, whether the rostral is paired or unpaired. A bony, spike-like structure, directed anteroventrally, is positioned on the anterior out- line of the presumed rostral (Fig. 3, asls). It is unclear, whether it is a separate anatomical element (i.e. the ex- tremity of the ethmoid complex), or only a portion of the counterpart of a possibly paired rostral, and it is a result of the deformity of the rostral region of the cranium. Dermopterotic, parietal and frontal: This bone-complex (Fig. 3, DerPaFr) forms the major part of the skull roof; how- ever, the sutures cannot be separated properly due to the poor preservation. A crack runs through the posterior part of the DerPaFr (see Fig. 3). Extrascapulars: These plate-like dermal ossifications (Fig. 3, Esc) are arranged in a series behind the dermopterotic- parietal-frontal region. They are rectangular in shape, as typ- ical for species of Dapedium. The series includes at least five plates on the observable side of the skull. Circumorbitals: The series of circumorbital bones comprises bones surrounding the orbit dorsally, ventrally and caudally, including the supraorbital, dermosphenotic, infraorbitals and suborbitals: Fig. 2 Dapedium sp. (V.10279; upper: V.10279-B—lower: V.10279-A) Supraorbital: Not preserved in the studied specimen. from the Toarcian Úrkút Manganese Ore Formation (Úrkút, Hungary) Dermosphenotic: This bony plate is placed dorsally to the orbit (Fig. 3, Dsph). It is rectangular in shape, and it fits later- Genus: Dapedium Leach, 1822 ally to the DerPaFr-complex. Due to its preservation, sensory canals of dermosphenotic cannot be investigated in V.10279. Dapedium sp. Infraorbitals: The infraorbital series (Fig. 3, Io) is in- Figs. 2, 3, 4 and 5 completely preserved. It includes rectangular bone-plates, placed ventrally around the orbit. However, this portion of Referred material: One individual (V.10279) preserved in a the skull is also heavily damaged, and only some phosphoritic nodule, in lateral aspect. infraorbitals are preserved in their original position and with original outline. Endochondral neurocranium Suborbital: Similarly to other circumorbital bones, these elements are also rectangular in shape (Fig. 3, Sor). Outlines The endochondral neurocranium is poorly preserved, and almost of some damaged suborbital plates are observable. The totally covered by dermal cranial ossifications. Neurocranial boundary of the infraorbitals and suborbitals is not clear due parts are visible in the orbit, and less clearly in the postorbital to the preservation level of this skull region. region. The orbital portion of the braincase is represented by a Parasphenoid and vomer: No remains of these bones can be greyish bone element, which is tentatively referred as the seen in V.10279. basisphenoid, which dorsally continues into the interorbital sep- tum (Fig. 3, ios). A large and circular interorbital fenestra is seen posteriorly to the interorbital septum (Fig. 3,iof). Visceral skeleton

Dermal neurocranium Mandibular arch: endochondral elements

Rostral, nasal and antorbital: This part of the cranium is Palatoquadrate and articular: No remains of these bones deformed, the outline of the rostral, nasal, and antorbital can be seen in V.10279. Palaeobio Palaeoenv

Fig. 3 a Cranium of V.10279 (on the left: V.10279-B—on the right: extrascapular series; Gu gular plate; Ino interoperculum; Io infraorbital V.10279-A). b Line drawings of the same views. ano anterior nasal series; iof interorbital fenestra; ios interorbital septum; Mx maxilla; Op opening; AnSuSp co-ossified angular-supraangular-splenial; asls anterior operculum; Pro preoperculum; PscStlPsu region of posttemportal- spike-like structure on the suggested rostral; Brr branchiostegal rays; Cle supracleithrum-presupracleithrum; Pmx premaxilla; Pscl postcleithrum; cleithrum; De dentale; DerPaFr co-ossified dermopterotic-parietal- RoNaAnt region of rostral-nasal-antorbital; Sbo suboperculum; Sor sub- frontal; ?dptee dermopalatine teeth; Dsph dermosphenotic; Esc orbital series. Dotted lines refer to uncertain bone outlines

Mandibular arch: dermal elements caudal margin of the maxilla is hardly separable from the anterior margin of the anteriomost infraorbital elements. Premaxilla: This paired element forms the tip of the snout Dermopalatine: In V.10279, only a few poorly preserved teeth (Figs. 3 and 4, Pmx). The premaxillae are bordered dorsally by are referred to the possible dermopalatine (Figs. 3 and 4, ?dptee). the rostral (or rostrals), and laterocaudally by the maxillae. In These teeth are positioned dorsally to the rostral end of the max- V.10279, the premaxillae are damaged. Premaxillary teeth of illa, and since maxilla of Dapedium usually does not bear teeth, V.10279 are of simple morphology, and they are unicuspid, con- here, these teeth are regarded to belong to the dermopalatine ical with blunted tip, decreasing in height posteriorly (see Fig. 4). (however, the boundary between the possible dermopalatine and Maxilla: The maxilla is wedge-shaped, runs anteroposteriorly the maxilla is obscure). Similarly positioned dermopalatine and broadens posteriorly (Figs. 3 and 4, Mx). In V.10279, the teeth are figured by Thies and Hauff (2011), figs. 1 and 3). Palaeobio Palaeoenv

Fig. 4 UpperandlowerjawofV.10279(a V.10279-A—b V.10279-B). Note the conical, unicuspid teeth. De dentale; ?dptee dermopalatine teeth; Mx maxilla; Pmx premaxilla

Dentary: The dentary of V.10279 is independent (Figs. 3 Dentary of V.10279 bears simple, unicuspid, conical and 4, De), and separated from the co-ossified angular, teeth with blunted tip, decreasing in height posteriorly supraangular and splenial (Fig. 3, AnSuSp). The inde- (see Fig. 4). An anterior tooth bends distally. pendent dentary in the early Toarcian Dapedium species Coronoids: No coronoids can be seen in V.10279. has been reported by several authors (e.g. Thies and Herzog 1999; Thies and Hauff 2008, 2011). This varia- Hyoid arch: endochondral elements tion of the dermal bones of Dapedium was considered as intraspecific variability by Thies and Herzog (1999). The Only a few barely visible bone-fragments can be referred with anteriomost end of the lower jaw cannot be observed. certainty as ventrorostral parts of the ceratohyal. Palaeobio Palaeoenv

Hyoid arch: dermal elements anteriorly to the last branchiostegal ray. Its exact shape cannot be determined. Operculum: The relatively well-preserved operculum (Fig. 3, Preoperculum: The preoperculum (Fig. 3,Pro)isposi- Op) posteriorly rests against the cleithrum, and ventrally tioned dorsally to the interoperculum. It is horizontally against the supracleithrum. According to measurements taken elongated and slender, albeit hardly visible on V.10279. on both part and counterpart, based on the preserved outline of This element is a bony tube for the vertical branch of the operculum, its rostral and ventral borders are forming an the preopercular canal (Thies and Waschkewitz 2015). obtuse angle of 123° and 127°. This bone element is 1.4× Branchial apparatus: The branchial apparatus is not visible higher than wide. on V.10279. Suboperculum: This bone (Fig. 3, Sbo) has slightly convex caudoventral and rostroventral margins; it borders the opercu- Postcranial skeleton lum with a nearly straight dorsal margin, which ends in an acute angle dorsorostrally. Axial skeleton: The axial skeleton is covered by scales; no Interoperculum: The interoperculum (Fig. 3, Ino) is simple, internal remains of it are observable. elongated tongue-shaped in lateral view. Anteriorly, it ends Endochondral shoulder girdle: Endochondral elements of near to the caudoventral end of the lower jaw. The dorsolateral the shoulder girdle of V.10279 cannot be observed. surface articulates with the medial surface of the preoperculum. The interoperculum is bordered ventrally by the first branchiostegal ray. Dermal shoulder girdle Branchiostegal rays: At least six branchiostegal rays (Fig. 3, Brr) are present as anteroposteriorly elongated bone elements. Posttemportal, supracleithrum and presupracleithrum: They converge to the suggested position of ceratohyal, behind These bones are damaged and/or partially covered by other the gap between the gular and the caudoventral border of the bone elements; therefore, they are not distinguishable (Fig. 3, lower jaw, under the anterior end of the interoperculum, PstSclPsu). The presence of presupracleithrum has been re- forming a fan-like structure. This is a typical structure of ported in D. pholidotum, D. politum and D. punctatum (Wenz branchiostegal rays for Dapedium (see figures of Thies and 1967; Thies and Waschkewitz 2015). In Dapedium, the plate- Hauff 2011 and Thies and Waschkewitz 2015). like posttemporal connects the dermal shoulder girdle with the Gular plate: Themediangularplate(Fig.3, Gu) is positioned skull roof. Caudally, it is bordered by the squamation, while ventrally to the ventrocaudal end of the lower jaw, and rostrally by the extrascapular series.

Fig. 5 a, b Pectoral fin of specimen V.10279 (a V.10279-A—b V.10279-B). c, d Anal fin of specimen V.10279 (c V. 10 27 9- A—d V.10279-B) Palaeobio Palaeoenv

Cleithrum: The cleithrum of V.10279 (Fig. 3,Cle)is V.10279. The number of postcleithra varies in species poorly preserved and heavily damaged. The preserved of Dapedium (Thies 1988; Thies and Hauff 2008;Thies portion indicates that it does not differ from that of and Hauff 2011; Thies and Waschkewitz 2015). other Dapedium species. The cleithrum is a narrow, rostrocaudally bent bone element. The exposed dorsal end terminates at around the midpoint of the caudal margin of the operculum. The ventral end is fragmen- Paired fins tary, but it would have most likely ended under the branchiostegal rays. Pectoral fins: On V.10279, only the base of left pectoral fin is Postcleithrum: Remains of postcleithra in V.10279 are preserved (Fig. 5a, b). Further anatomical details of the pec- obscure, since this region is heavily damaged. Some toral fin remain obscure. The pectoral fin is positioned high on faint remains of the margin of a possible postcleithrum the flank, and behind the fragmentary ventral section of the (Fig. 3, Pscl) are present on the counterparts of cleithrum.

Fig. 6 Measurements of the squamation of specimen V.10279-A. Numbers show the measured areas Palaeobio Palaeoenv

Pelvic girdle and fins: Part of the ventral part of the body of the skull bones, but it differs in having rounded to slightly V.10279 is missing, probably resulting in the loss of the pelvic convex posterior scale margins, and lighter scale cover, in girdle and the pelvic fins. contrast to the thick, rhomboidal ganoid scales of V.10279. The operculum of the Triassic species D. ovalis is at least twice as high as long (Tintori 1983), whereas V.10279 has Unpaired fins an operculum only 1.4× higher than wide. In addition, D. ovalis has shorter and fewer branchiostegal rays, compared : No remains of the dorsal fin are seen in V.10279, to the Úrkút dapediid (Gorjanović-Kramberger 1905; Tintori as it may be covered by the matrix, but further preparation of 1983). The head of Dandya is proportionally much larger than the specimen is too risky due to its condition. that of all other dapediid genera (see Gorjanović-Kramberger Anal fin: The preserved parts of the anal fin suggest a seam- 1905,fig.25;Tintori1983, fig. 3; Schultz 2013,pl.22,fig.1). or hem-like anal fin, comprising at least 14 lepidotrichia Scopulipiscis is an extremely large-sized dapediid from the (among them two are almost fully covered by the matrix), Rhaetian, with a neurocranium that reaches 17 cm in length nearly equal in size (Fig. 5c, d). (Latimer and Giles 2018). This species is substantially differ- Caudal fin: The caudal fin of V.10279 is completely missing. ent from the Úrkút specimens, which has a full cephalocaudal Scales and squamation: The trunk is fully covered by shiny, length of 233 mm, and is Toarcian in age. For these reasons, rhomboidal ganoid scales. The preserved scales are arranged V.10279 does not belong to any of these four genera. in 38–39 vertical and 29–30 horizontal rows (these numbers The genus Tetragonolepis has a ventrally much more pro- are approximate only, because the crack surface between the tuberant body (Thies 1991) compared to the Úrkút dapediid. left and right counterparts is irregular; hence, in some cases, it The trunk scales have clearly different proportions depending cannot be established, which side a scale row or section of a on their dorsoventral and caudorostral position (Thies 1991, scale row belongs to). There are incomplete vertical rows text-fig. 37), whereas V.10279 has only slightly variable above and below the shoulder girdle. The vertical rows are squamation. The branchiostegal rays of Tetragonolepis slightly curved. The scales have simple, unserrated outline. semicintca posteriorly decrease in size (Thies 1991), whereas The better preserved scales have a smooth surface, and the V.10279 bears branchiostegal rays that are nearly equal in size ganoine is developed as a single, continuous layer. The size and shape. According to Jain (1973), Tetragonolepis oldhami and proportions of the scales vary according to their position displays three branchiostegal rays that become progressively on the body (Fig. 6; measurements were taken on body parts larger from the anterior, unlike those of the Úrkút specimen. with less fragmentary squamation to indicate the relative size Finally, Tetragonolepis spp. are generally much smaller (with and morphology of scales in different regions). Dorsal and maximal body length of 18 cm; Thies 1991) than the Úrkút ventral ridge scales are present but poorly preserved. specimen. Paradapedium was first described in detail by Jain (1973), from the Lower Jurassic of India (through its type species P. Taxonomic comparisons and remarks egertoni). Branchiostegal rays are diagnostically inconspicu- ous in this genus, which is different from V.10279. In addition, The preserved anatomical features of the Úrkút dapediid allow the Úrkút dapediid has much less protuberant ventral abdom- its generic assignment and distinction from the eight other inal region, than Paradapedium (cf. Jain 1973,text-figs.3,5, dapediid genera (Gibson 2016; Latimer and Giles 2018). 6 and pl. 14). Based on the fossil record, among these Hemicalypterus, Eastman (1914)statesthatHeterostrophus (originally de- Sargodon, Dandya and Scopulipiscis seem to went extinct at scribed as Homoeolepis in his work) is similar to the end of Triassic, whereas the Úrkút specimen is Toarcian in Tetragonolepis, but it can be distinguished by its less protu- age. Apart from the difference in age, Hemicalypterus has a berant ventral body region, lower positioned pectoral fins, and cycloidal body, with scaleless posterior body half (Gibson having more scales in the vertical scale series below the 2016), whereas squamation of Sargodon (whose body shape vertebral axis. The specimen figured by Eastman (1914)as also differs from that of V.10279) becomes extremely thin Homoeolepis suborbiculata was re-described by Lambers posteriorly (Tintori 1983). In contrast to these two genera, (1999)asHeterostrophus latus. Woodward (1929)statesthat the entire body of the Úrkút dapediid is covered by shiny ganoine is either thin or almost absent on the external surface ganoid scales, only slightly variable in proportion. of the scales of another species of this genus, Heterostrophus Moreover, Hemicalypterus has multicuspid premaxillary and phillipsi, whereas scales of Dapedium are covered by a thick, dentary teeth (Gibson 2015), unlike V.10279 which shows well-developed layer of ganoine. According to this author, the simple, unicuspid teeth. According to Tintori (1983), maxilla of both H. latus and H. phillipsi bears teeth. Although Dandya is rather similar to Dapedium in the arrangement of this feature is not clearly seen in V.10279, here, we suggest Palaeobio Palaeoenv

Fig. 7 Stratigraphic ranges of the nine genera assigned to Dapediidae, Waschkewitz 2015; Thies and Hauff 2011; Tintori 1983. Tetragonolepis: resolved at stage level. Compiled from the following sources: Dandya: Bandyopadhyay et al. 2010; Bassani 1886;Münster1841; Corroy 1934; Tintori 1983; Gorjanović-Kramberger 1905; Schultz 2013. Sargodon: Kear Delsate et al. 2002;Thies1991; Jain and Roychowdhury 1987;Prasadand et al. 2010 and references therein; Boni 1937;Tintori1983, 1998; Chalupová Manhas 2007;Jain1973; Boulvain et al. 2000. Paradapedium: 2009; Godefroit et al. 1998; Boulvain et al. 2000;Schultz2013;Korneisel Bandyopadhyay et al. 2010;PrasadandManhas2007;Jain1973;Jainand et al. 2015;Nordénetal.2015. Hemicalypterus:Gibson2015. Scopulipiscis: Roychowdhury 1987. Heterostrophus:HudsonandMartill1991;Lambers Latimer and Giles 2018. Dapedium: Gorjanović-Kramberger 1905; Godefroit 1999. Aetheolepis: Bean 2006; Woodward 1895b; Veevers 2000.Question et al. 1998; Maxwell and López-Arbarello 2018; Schultz 2013; Thies and marks refer to unfigured or questionable reports Palaeobio Palaeoenv that its maxilla is toothless. The body size (about 45 cm in full- In summary, the reasons discussed above provide a solid body length) of the two species of Heterostrophus described basis to refer V.10279 to Dapedium. However, as preservation by Woodward (1929) is much larger than that of the Úrkút hinders observation of some diagnostic features, an assign- dapediid. Nevertheless, Heterostrophus is very similar to ment to any species is not attempted, until other specimens Dapedium in the proportions of the squamation, and in gen- provide additional data. eral body shape, but differs in its stratigraphical range (see Fig. 7). Aetheolepis has a much more diamond-shaped body and Discussion different fin proportions, compared to the Úrkút dapediid. Aetheolepis bears ganoid scales on the anterior half of the Overview of the fossil record and stratigraphic distribution body, but amioid-type scales posteriorly (Gibson 2016), un- of dapediids like V.10279. Among the general characters of Dapedium, the hypsisomatic Here, we discuss the occurrences and stratigraphic range of body, the interlocking rhomboidal ganoid scales, the relatively each of the nine genera assigned to Dapediidae by Thies and small mouth and the hem-shaped anal fins are visible on Hauff (2011), Gibson (2016)andLatimerandGiles(2018). V.10279. Thies and Waschkewitz (2015) summarised the diag- The small bodied Dandya (first described as Spaniolepis by nostic features for Dapedium (amended from Wenz 1967 and Gorjanović-Kramberger 1905) has been reported from the Thies and Hauff 2011), of which only one can be observed on Norian of Lombardy (Italy) (Tintori 1983) and Salzburg V.10279: the number of branchiostegal rays between four and (Austria) (Gorjanović-Kramberger 1905). eight. Sargodon has been reported from several sites of Europe. V.10279 is slightly deformed rostrocaudally due to diagen- Boni (1937) assigned molariform teeth to Sargodon from esis, and/or post-lithification stress. This makes the taxonom- Rhaetian strata of northern Italy. Further isolated teeth of ically important characters hard to observe clearly in some Sargodon are recorded from the Rhaetian beds of England, areas (e.g. in the nasal region). Nonetheless, body shape of France and Germany (Tintori 1983). Chalupová (2009)fig- V.10279 falls well within the morphological range of ured both molariform and incisiform teeth assigned to Dapedium, since the genus shows variability in body shape, Sargodon tomicus from the Rhaetian of Slovakia. Rhaetian specimens could be fusiform, ellipsoidal or even cycloidal beds of Syren (Luxembourg) also yielded isolated teeth of S. (Thies, pers. comm.). The Toarcian age of the specimen falls tomicus (Godefroit et al. 1998). S. tomicus is known from the into the known range of Dapedium. Rhaetian Mortinsart Formation of Lorainne (Belgium) Measurements were taken on the scales of V.10279-A. (Boulvain et al. 2000). Storrs (1994), Korneisel et al. (2015) Thies and Waschkewitz (2015) measured four areas of the and Nordén et al. (2015) also reported Sargodon from the squamation in various species of Dapedium,usedhereto Rhaetian of England. Tintori (1983)reportedwell-preserved compare with V.10279. The three measured areas of specimens of S. tomicus from the Norian of Lombardy. From V.10279-A are not the same as those of Thies and older strata, Kear et al. (2010) reported unfigured specimens Waschkewitz (2015), because our aim was to demonstrate of Sargodon from the Middle-Upper Triassic (upper Anisian the variability of scale proportions of the Úrkút specimen. to lowermost Carnian) Jilh Formation of Saudi Arabia, but For this reason, our method of using the measurements is also this occurrence, possibly the oldest one for the whole group, different from that of Thies and Waschkewitz (2015). The remains doubtful. highest (or deepest) measured scales of V.10279-A are posi- Hemicalypterus is only known from the Upper Triassic tioned on the posterior flank, near to the lateral line. The re- (Rhaetian) part of the Chinle Group in southeastern Utah, sults (Fig. 6) show that the length/height (l/h) ratio of the USA (Schaeffer 1967;Gibson2015, 2016). scales slightly decreases posteriorly. No l/h measurements Scopulipiscis is a large-sized (approximate body length of of the squamation were taken in dapediid genera with 2 m) dapediid reported from the Upper Triassic (Rhaetian) of body shape similar to Dapedium (Paradapedium, the Kössen Formation at Schesaplana, Grisons, Switzerland Tetragonolepis, Dandya), but figures of Jain (1973)and (Latimer and Giles 2018). Tintori (1983) suggest that l/h ratio in these genera sharp- The Úrkút occurrence of Dapedium is in accordance with ly decreases dorsoventrally (i.e. the highest scales are po- the abundance of the genus in the Toarcian. Maxwell and sitioned on or near to the belly region). Heterostrophus López-Arbarello (2018) recognises 15 valid species within shows very similar scale proportions to that of Dapedium, the genus, ranging from the Upper Triassic (Norian) to the with slight variability in different areas of the body sur- Middle Jurassic (Aalenian) (see Maxwell and López- face, but the Úrkút dapediid is excluded from Arbarello 2018, table 1 and references therein). Thus, the Heterostrophus for other reasons (see above). No infor- Norian to Aalenian range of Dapedium is well-established mation of the squamation of Scopulispiscis is available. from a remarkable fossil record in Lagerstätten and Palaeobio Palaeoenv formations enabling exceptional preservation (Zorzino dapediids have not been reported from the site (Williams Limestone, Blue Lias, and Opalinus Clay). et al. 2015). This formation would be expected to yield Tetragonolepis has been often synonymized with dapediids, as it is coeval with the Posidonia Shale and paleo- Dapedium, especially in works dating back to the nineteenth geographically not far from it; therefore, the lack of dapediid century. Evaluation of these reports is extremely difficult and finds in the Strawberry Bank fossil record is somewhat unex- some confusion is apparent (e.g. see synonymy lists of pected. It may be accounted for by collection failure, as the Woodward 1895a and Schultz 2013). Here, we follow Thies fossil locality is now buried and collecting is no longer (1991), who considers Tetragonolepis as a distinct genus with possible. With regard to the above, a significant gap in the two valid species, T. semicincta and T. oldhami, known from fossil record of dapediiforms in the Middle Jurassic may not the Toarcian to the ?Aalenian (Jain and Roychowdhury 1987; be surprising. This likely relates to the overall lack of fossil Jain 1973;Thies1991;PrasadandManhas2007; localities preserving whole-bodied actinopterygian specimens Bandyopadhyay et al. 2010). Tetragonolepis sp. was reported (Smithwick and Stubbs 2018). The lack of Bajocian-Bathonian (but not figured) from the Toarcian Grandcourt Formation of finds predicts further discoveries, as Heterostrophus and Lorainne, Belgium (Boulvain et al. 2000). A questionable Aetheolepis are unquestionable members of the order report of Tetragonolepis from the Hettangian of Fontenoille Dapediiformes. (Belgium) is based on a single isolated tooth (Delsate et al. 2002,pl.15,fig.c). Dapediids and the end-Triassic and Toarcian mass extinctions Paradapedium is only known from the upper Kota Formation (Toarcian-?Aalenian) of India (Jain 1973;Jain According to the available data, five known dapediid genera and Roychowdhury 1987; Prasad and Manhas 2007; existed in the Late Triassic: Dandya, Sargodon, Hemi-calypterus, Bandyopadhyay et al. 2010). Scopulipiscis and Dapedium. Based on the fossil record, among Eastman (1914) described specimens of the genus these taxa, only Dapedium survived the end-Triassic mass Heterostrophus, originally under the name of Homoeolepis. extinction. The other dapediid genera Tetragonolepis, Heterostrophus is known from the (Lower Oxford Paradapedium, Heterostrophus and Aetheolepis originated in the Clay, England; Hudson and Martill 1991), and, with a strati- Jurassic, i.e. after the end-Triassic mass extinction (Fig. 7). graphical gap for the Oxfordian, also from the upper The end-Triassic mass extinction is considered as one Kimmeridgian—lower (Solnhofen, Germany; of the five biggest mass extinction events, with data sug- Lambers 1999). gestingextinctionlevelsofupto80%amongthemarine Aetheolepis was described from a single locality, the skeletonized invertebrate species lost (Sepkoski 1996). Kimmeridgian Talbragar beds of Australia (Woodward 1895b). Synchronicity of mass extinction and volcanism of the The fossil record of Dapedium in particular, and dapediids in Central Atlantic Magmatic Province in the Triassic- general, is clearly biased by the Lagerstätten effect, with the Jurassic boundary is well-established (Pálfy et al. 2002; majority of occurrences of articulated specimens known from Pálfy 2003). Large amount of carbon dioxide released formations amenable to exceptional preservation. Apart from from volcanoes resulted in extreme greenhouse warming, taphonomic bias, the predominance of European occurrences ocean acidification and anoxia (Hautmann 2004, 2012; may also represent an additional bias introduced by geographi- Hautmann et al. 2008; van de Schootbrugge et al. 2009; cally uneven sampling, with Old World localities with a long Pálfy and Kocsis 2014). Moreover, volcanism might have history of study and superior sampling effort heavily overrepre- caused sudden warming of deep waters as well that result- sented. Australia, India and the USA only contribute scattered ed in methane-release (Pálfy 2003). Both marine and ter- localities to the known geographic distribution of the group; thus, restrial communities showed drastic changes across the the notion of a European (i.e. westernmost Tethyan) centre of Triassic-Jurassic boundary (Benton 1995). dapediid evolution may represent an artefact caused by sampling The radiation of Dapedium occurred after the end-Triassic bias. However, the recently described Ya Ha Tinda Lagerstätte in mass extinction (Smithwick 2015; Smithwick and Stubbs the Toarcian of Alberta (western Canada) has not yielded 2018). A compilation of Early Jurassic occurrences of dapediid remains (Martindale et al. 2017). Dapedium from Europe shows that these fishes were wide- Remarkably, the confirmed range end points of spread in the northwest European epicontinental sea in this dapediids are also related to Lagerstätten, as the first epoch. Their success could be related to the generalist- undisputed occurrence of the group is from the Norian durophagous feeding strategy and the deep, flattened body Zorzino Limestone and the youngest occurrence is re- shape (Thies and Hauff 2011; Fletcher et al. 2017; Stumpf corded from the Kimmeridgian-Tithonian Plattenkalk of et al. 2017; Smithwick and Stubbs 2018), which provided a Solnhofen. Also notable, however, that the Toarcian wider range of available prey and high manoeuvrability for Strawberry Bank Formation Lagerstätte (Somerset, UK) these fishes after the end-Triassic mass extinction (Bellwood yielded a various actinopterygian taxa, but up to now, and Hoey 2004; Smithwick 2015). Ammonites could have Palaeobio Palaeoenv served as a food source in near surface waters for generalist- (Tintori 1983) and grinding palatal teeth. This indicates that durophagous (and scavenger) dapediids, including the genus Sargodon fed on invertebrates, possibly using the bifid Dapedium, before and after the end-Triassic mass extinction. marginal teeth to pick up shelly invertebrates (e.g. gastro- This is partially supported by a Dapedium individual pods, bivalves, brachiopods) from the substrate, then fossilised in the body chamber of a Lytoceras sp. specimen, crushed their hard exoskeletons with the grinding palatal found in the Toarcian Posidonia Shale (Thies and Hauff teeth (Tintori 1983;Gibson2015). Sixty-three percent of 2011), and suggested as proof of scavenging feeding strategy, marine invertebrate taxa became extint in the end-Triassic rather than predation. This inference is in agreement with mass extinction (Alroy 2008). Seventy-one percent of Andrew et al. (2010), who suggested that fish could not easily articulated brachiopod genera and 40% of marine bivalve manipulate ammonite shells to remove the soft internal parts. genera became extinct, while gastropods also suffered Smithwick and Stubbs (2018) provide the most recent significant losses (Hautmann et al. 2008). Such great loss comprehensive analysis of fishes through the end-Triassic of invertebrate taxa, their food source could have been an mass extinction event and show little change across the important driver in the extinction of Sargodon in the boundary in terms of diversity, body shape or ecomorphology end-Triassic. Hautmann et al. (2008) noted that several in actinopterygians. One major change, however, occurred in bivalve families switched from aragonitic to calcitic dapediids: after the end-Triassic mass extinction, Dapedium shells across the Triassic-Jurassic boundary. The shift was shown to radiate into a novel area of functional from weaker aragonite to harder calcite skeleton in its morphospace by developing a unique jaw morphology not prey may also have contributed to the demise seen in any other Early Jurassic fish genus (see also in of Sargodon. Smithwick and Stubbs 2018, fig. 2). This finding supports that Hemicalypterus is regarded as a herbivore with specialised, the jaw and the feeding mode were important factors in their multicuspid dentition that probably exploited a nektobenthic survival and radiation after the extinction event. feeding niche by using its multicuspid teeth to harvest algae or We suggest that the effects of the end-Triassic mass extinc- other attached plants and organisms from a rocky substrate tion may also be reflected in other changes in the anatomy of (Gibson 2015). These food sources may be sensitive to acid- dapediid fishes. Extinction of taxa with light squamation (i.e. ification and anoxia, both thought to have occured in the end- incomplete body squamation, thin and/or non-ganoin Triassic, leading to decrease of food source during the mass squamation, or scales only poorly ornamented by ganoine), extinction event. A specialist feeder is more vulnerable to and the survival of Dapedium, a form with thick, full-body rapid environmental changes than a generalist durophage ganoid squamation in the end of the Triassic is a clearly (Smithwick 2015 and references therein), possibly leading to emerging pattern. A possible reason for the extinction of some the extinction of Hemicalypterus, as there is no record of taxa could have been the less effective protection of the in- Hemicalypterus after the end-Triassic mass extinction event complete and light squamation against predators. Ganoid (Gibson 2015). scales are heavy and difficult to penetrate (penetration The single available specimen of Scopulipiscis is a resistance of scales of living ganoid taxa has been neurocranium with associated dermal elements (Latimer and investigated by, e.g. Bruet et al. 2008; Song 2011; Sherman Giles 2018); hence, no teeth and scales are preserved, preclud- et al. 2016); therefore, bearing a well-closing, ganoid scale- ing inferences about its feeding habit. Its extremely large size armour would also have been likely to be a successful strategy (c. 2 m in length) allows speculation that selectivity against against predators. After the end-Triassic mass extinction, ma- large size may have been a factor in the end-Triassic extinction rine reptiles, such as sauropterygians, ichthyosaurians and that also wiped out Sargodon, which reached 1 m in full-body thalattosuchians, played important roles in marine ecosystems length (Tintori 1983). and could have been potential predators preying on dapediid A generalist-durophagous feeding strategy could have pro- fishes (Thorne et al. 2011; Stubbs and Benton 2016). vided a wider range of prey for taxa with simple, unicuspid, Scales of Dandya were ornamented by only scattered, styliform teeth such as Dapedium, Tetragonolepis and small spots of ganoine, rather than a continuous ganoine- Paradapedium during and after end-Triassic mass extinction. layer (Tintori 1983), scales of Sargodon become extremely This allowed Dapedium to radiate and fill vacant ecospaces, thin posteriorly (Tintori 1983) and the posterior flank of previously occupied by taxa that vanished at the end-Triassic Hemicalypterus is devoid of scales (Gibson 2016). As Fig. 7 mass extinction (Bellwood and Hoey 2004; Smithwick 2015; illustrates, only Dapedium, a genus with full-body ganoid Smithwick and Stubbs 2018). Moreover, the laterally flat- squamation, survived the end-Triassic mass extinction. tened, deep (hypsisomatic) body shape of Dapedium indicates Another possible reason for the extinction of Sargodon that these fishes were well-adapted to maneuvering (Poyato- and Hemicalypterus could have been their food preference. Ariza 2005; Fletcher et al. 2017; Stumpf et al. 2017). The Dentition of Sargodon included bifid incisors on the same reasons may explain the emergence of Tetragonolepis premaxilla and dentary, usually with a V-shaped notch and Paradapedium (taxa similar to Dapedium in dentition and Palaeobio Palaeoenv body shape) in the Jurassic. Although dental evidence might Conclusions suggest ecological niche overlap, differences in morphologi- cal adaptations in Dapedium and Tetragonolepis (as well as The Dapedium specimen from Úrkút is the first articulated the Early Jurassic neopterygian , which is also con- Mesozoic fish body fossil from Hungary that is described in sidered as a facultative durophagous feeder) are likely con- detail. The occurrence of Dapedium in the Úrkút Manganese nected with their foraging mode and, consequently, in the Ore Formation represents the first report of the order segregation of available food resources (Stumpf et al. 2017). Dapediiformes from Hungary. The preserved cranium reveals After the end-Triassic mass extinction, bifid marginal teeth re- important characters, although species-level identification is occurred in various Liassic Dapedium species, such as D. hindered by suboptimal preservation of some diagnostic fea- politum, D. radiatum, D. orbis, D. dorsalis, D. colei and tures. The general body morphology, details of the squamation D. granulatus (Woodward 1895a; Thies and Hauff 2011), and preserved features of the skull allow its unambiguous suggesting that changes occurred in the diet of dapediids. assignment to Dapedium and distinguish the Úrkút specimen A third possible reason for the disappearance of some from other dapediiform genera, in agreement with its Toarcian dapediiforms in the end-Triassic is the global reef crisis driven age. The Úrkút locality extends the known geographic distri- by climate warming. The end-Triassic warming and possible bution of the genus and the order. ocean acidification triggered a collapse of metazoan reefs We speculate that the disappearance of exclusively Late (Hönisch et al. 2012; Pandolfi and Kiessling 2014). 117 reefs Triassic dapediid genera coincided with the end-Triassic were recorded in the Norian-Rhaetian (Kiessling et al. 1999), extinction event, although a patchy fossil record makes and the sudden disappearance of these reefs is one of the most this difficult to determine unambiguously. Selective ex- obvious indicators for the biological crisis at the Triassic-Jurassic tinction or survival of dapediid genera during the end- boundary (Pálfy and Kocsis 2014).Thecollapseofthe Triassic event was likely related to their feeding strategy reef ecosystems as habitats could have been a major driv- and squamation, and may also be connected to the global er for the extinction of the dapediiform taxa, less capable reef crisis. for adaptation. The exceptional Toarcian fossil record of dapediids is Dapedium is the only known dapediid genus surviving the likely explained by the Lagerstätten effect. In contrast to end-Triassic extinction (Fig. 7), and generic diversity of the the end-Triassic event, the Jenkyns event or T-OAE group only approached the Rhaetian level in the Toarcian, caused no genus-level extinction among the dapediids as where two other genera (Tetragonolepis and Paradapedium) all three genera known from the Toarcian survived into are also recorded. Dapedium is not only the longest-ranging, theAalenian.Thedifferencemaybeexplainedbyresil- but also the most speciose genus of the group, with excep- ience from adaptation evolved during the first of these tional records of both the Sinemurian and Toarcian. two similar, multi-stressor crises. The lack of Bajocian- Although the Lagerstätten effect may distort the species- Bathonian occurrences serves as a reminder of the incom- level diversity history, it is remarkable that all three genera pleteness of dapediid fossil record which leaves a degree known from the Toarcian (Dapedium, Tetragonolepis and of uncertainty in any reconstruction of their diversity his- Paradapedium) survived into the Aalenian (Fig. 7). The tory but underlines the significance of each new find. Jenkyns event (or Toarcian Oceanic Anoxic Event) clearly contributed to the exceptional preservation in the Posidonia Acknowledgements Open access funding provided by Eötvös Loránd Shale and correlative anoxic sediments (including the Úrkút University (ELTE). We thank Lynne Bean, Lóránt Bíró, John Clarke, Martin Ebert and István Főzy for providing literature sources, photo- Manganese Ore Formation), yet the coeval cascade of envi- graphs and helpful information. We are grateful to Emese Réka Bodor ronmental changes did not cause genus-level extinction and Detlev Thies for their constructive suggestions. We also thank László among the dapediids. The Jenkyns event is well known to Makádi and Bálint Szappanos for their technical assistance. Contributors be an episode of rapid environmental changes that bears to the Paleobiology Database are acknowledged here for compiling oc- currence data from relevant literature. Constructive reviews by Lionel many similarities to the end-Triassic event. Volcanism of Cavin and an anonymous reviewer have greatly improved the manuscript. the Karoo-Ferrar large igneous province is thought to have triggered global warming, changes in ocean chemistry, in- Funding information Our work was supported by the National Research, cluding anoxia, possible ocean acidification, and a second- Development and Innovation Office (Grant No. K116665), the Hungarian order extinction event (Jenkyns 1988, 2010; Harries and Natural History Museum, the Eötvös Loránd University and the ELTE Dinosaur Research Group. This is MTA-MTM-ELTE Paleo contribution Little 1999; Pálfy et al. 2002; Hönisch et al. 2012). In no. 271. contrast to the end-Triassic event, however, the Jenkyns event did not cause genus extinction among the dapediids. Compliance with ethical standards This suggests that acquired traits and adaptations evolved during the preceding multi-stressor event may have Conflict of interest The authors declare that they have no conflict of helped surviving the next crisis during the Toarcian. interest. Palaeobio Palaeoenv

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